What is the Moment of a Force? - CSEC Physics | Junior Roberts
Junior Roberts
https://www.youtube.com/watch?v=i2mdbUOhRi0

Transkript (automatisch erstellt)

0:00 okay all right so we're talking about moments we'll continue with that right now as we say let's just say we have an object like
0:08 this let's just start our door to recap if you have an object like this let's
0:14 say this is a um a plank right and we have that plank resting for example
0:23 on this thing right here right so in other words it's resting on this that is acting as a
0:33 as a what this is keyboard right so we have this acting absorber kind of
0:39 designed to polish a bit so we have this thing right here which is our pivot now when we have this situation right here
0:47 what we're going to see is that let's say we have a force that acts on this plank at the same of a force that acts
0:56 on this plank so in other words it's like somebody comes and sits right here so for example it's like we have a see-saw and we have
1:04 uh someone come and they sit on the seesaw at this point
1:11 right like so so they sit on a seesaw like this so what they're going to do now because they will have a mass
1:18 and they're in a gravitational field they're going to experience a force which is their weight so their weight will now be resting on
1:26 this plank right and produce this force that we direct downward so the weight will be directed downward right because as you know gravity is acting
1:38 downward so we're going to have a force let us say we call that f right so we have this force f right here acting on this object and as we can see
1:46 it is acting at some distance from this point right here which we say is our pivot so because
1:54 this force is acting at whatever distance this is from the pivot what we will see is that this pivot will
2:03 experience what we say is a turning effect or simply put we see that it is a moment so let me just refresh this again
2:13 so again what we're seeing is that we have this object right here right it is resting on this pivot right we have someone who comes and sits
2:21 on this side or sit anywhere could be anywhere once it is at some distance from the pivot
2:28 right in this case the distance d what we're going to see is that this object will experience a turning effect and that turning effect is what we refer
2:36 to as our moment okay yes sir right and we said no that that moment
2:44 which we call which will give the symbol t is simply equal to the product of whatever this force is
2:52 multiplied by this perpendicular distance d okay [Music]
3:00 third ontario information let me know what's going on with you yes sir i'm hearing what you think okay
3:08 good all right so just refresh yourself but it can be much more comfortable in terms of what we cover so this is what we have right here so
3:16 because of this force acting at this perpendicular distance from the line of action of the force so the force is going straight down and the
3:24 distance is taken perpendicularly to the direction of the force so now because of that situation what we see is
3:33 that this object will experience a turning effect and that turning effect is that turning effect will be about this
3:40 particular point okay and we can calculate the turning effect which is the moment by simply multiplying the force and whatever
3:48 perpendicular distance this is okay follow yes sir
3:59 so now let us do a little example let us say we say that this the weight of this person is let us say his weight is 500 newtons
4:09 right and he sitting at a distance let us say 1.6 meters from the pivot right so his weight is 500 newtons and it's sitting
4:19 at a distance of 1.6 meters from the pivot now based on this formula right here we can actually calculate the turning effect that will be produced
4:27 about this point by the weight of this person so now what we do know is we'll just simply
4:34 substitute in our formula and calculate so what we do know we're going to say that the force f is this value so we said 500
4:43 newtons multiplied by the perpendicular distance which is 1.6 meters and this works out to be what
4:51 800 800 what's the unit now matthew newton no of course
5:01 we're multiplying force in newtons and distance in meters newton meters right so that's how we calculate the moment of
5:13 a force all right okay
5:23 so let's do like two more examples let's do two more examples let's say um i'm gonna make this sort of a worded
5:31 one um let's say um a boy of
5:39 weight i'm gonna keep it simple wait let's say his weight is 520 newton
5:47 sat um let's say 1.5 meters
5:55 from the pivot of a seesaw
6:04 seesaw calculate the moment
6:14 due to the boy's weight boy's weight
6:22 about the pivot
6:29 all right let's see if we can do this uh from the people all right let's see if we can do this
6:42 all right so quickly try this one so we can discuss it okay so this is what we have right the
6:50 seesaw like so and this is the boy sitting right here this is the boy sitting right here like that
6:58 and he's sitting at a distance as you see 1.5 meters from the
7:04 pivot right and his weight is this value which is 520
7:12 newton so now since we want to find the moment or the turning effect about the pivot due to the weight of this person
7:20 we can say that the moment t is equal to is weight which is the force multiplied by the perpendicular distance d
7:28 now what we do from you know as well as plug in the values so we're going to say 520 newtons multiplied by 1.5
7:37 meters when you multiply these out we get 520 times 1.5 is what 700.00 18 80 newton meter
7:47 right so that's all we deal with this one all right now let me give you another one
7:55 i don't want to try you sure yes sir i got the correction i had 1.2 meters instead okay okay okay okay
8:06 all right next one no we're gonna say no um calculate
8:16 the moment due to
8:22 the weight of the girl of the girl in the diagram below
8:33 all right let's see if we can do this thing on diagram below um if she sits
8:44 if she sits let's say uh 1.2 meters from the
8:54 uh from one end from one from
9:00 [Music] one end of a uniform
9:08 let's say this is four meter blank pivoting
9:18 at its center so this one is a little more i've added
9:24 some more information so we have some let me just sketch the alternative you guys see what's going on so we're sorry
9:32 it's like where what's going on we have this thing okay and it is pivoting
9:41 like so all right we got it like that and we have a girl
9:48 this her pink so this girl sitting right here right like that
9:58 right that's the girl and as i said as you see right here she sits um uh what did i say again 1.2 meters so she sits 1.2 meters so
10:13 from where the girl is all the way to here
10:22 is simply 1.2 meters so let's say one point two
10:29 meters and this is a regular the weight of this curl is yes your weight is let's say 480
10:39 newtons all right so let's see what we take on this one
10:51 so again remember when we're calculating moments the distance is always
10:58 the perpendicular distance from the line of action of the force to the wire so you want to answer uh your phone answers it
11:11 yes sir [Music]
11:25 oh and again and again remember that the perpendicular distance
11:43 remember we'll talk about this up right here it's the perpendicular distance from the line of action of the force to the pivot
11:51 right so when we're looking at these questions we have to first determine where is the pivot so this is the pivot right here
11:58 so we need to know what's the perpendicular distance from where the girl sits right where our force will be acting to
12:05 the pivot so we need to determine this distance okay is there any way we can determine the
12:12 distance so we're going to divide um the four meters by eight
12:20 then top shot though one two okay all right so do that and see what happens
12:31 do you 84 newton newtons okay say what you got 384
12:42 actually all right so remember because it is right here that we have a uniform plank
12:52 uniform four meter plant and it is pivoted at the center and because this pivot at the center and it is four meter long then at the center
13:01 will be two meters so from here here is going to be two meters similarly from here there will
13:08 also be two meters now because the coil is sitting 1.2 meters from the end of the plank then the distance from
13:16 where she sits to the pivot which is what we need um for this calculation will have to be 0.8
13:25 meters right so now what we're saying is that the moment t must be equal to whatever force she applies to the planck
13:33 multiplied by a distance from the pivot so now we say this is 480 newtons multiplied by the perpendicular distance which is 0.8
13:44 meters and as we see once we calculate this we get what 384 284 um
13:53 is that okay